The WWE is always heel heavy, but since Ryback has turned heel, the only big guys who are currently faces are Randy Orton, Sheamus, and Kane. (Tons of Funk do NOT count, nor does the Awful Khali)
Ryback, Henry, Big Show, Sandow, Barrett, Cesaro, Reigns, and Langston (McIntyre doesn't count for the same reason Brodus and Tensai don't count).
Add to that the fact that Orton probably needs to turn heel to face Cena at Summer Slam (because the promotion needs a big name matchup between two totally over full time stars for the second biggest PPV of the year).
I mentioned in another post that I see Wade Barrett as a more natural face. He has a sense of humor and his background as a bareknuckle fighter is really easy for the crowd to get behind and have respect for. He's not a coward or a cheater, he's a tough guy with the heard of a British Lion. That's a really easy angle to sell and he really hasn't done a lot of bad things to earn heat.
On the other hand, Big E Langston is a heel in WWE but he's a face in NXT (because he's billed from Tampa, FL) though he's basically RyBlack and I think he would have a hard time getting over as a new version of a guy that is about to be buried by John Cena.
Big Show has spent more time in his career as a face, and he's really a more natural face because everyone knows he's a great guy in real life, but he's 40 and continuing to use him just holds back younger talent. Also the big man can only take so much more before his body breaks down. I want to see Big Show as a big, intimidating GM who enforces his rulings with a KO Punch whenever his authority is questioned. Beating Booker T in a match with the GM title on the line would be a pretty cool way to do that, since there has been a lot of storyline friction between the two of them.
Mark Henry is also old and he should never have been brought back after his contract expired following Wrestlemania, having Ryback lose to him and then giving him more time in the spotlight with so many better heel options was an awful decision. He's alright at playing his character, but in the ring he's worse than anyone on the roster except Khali.
Antonio Cesaro is probably the most talented guy in this group except Orton but he really wouldn't feel natural as a face. His recent backstage attack on Kingston was great and they need to run with it. I think he has what it takes to be a Super Heel on the level of the Iron Sheik. They just need to let him go and have him be evil as hell in and out of the ring. That's the kind of vicious over the top heel that WWE desperately needs and I wouldn't screw that up with a face turn. Similarly I can't see how you turn Damien Sandow's Nick Bockwinkel gimmick into anything but a classic heel persona.
To wrap it up, the Shield should stay together as a great heel team until after Wrestlemania 30 so Roman Reigns will remain a heel and a Yo-Yo face turn for Ryback will be even more damaging to him than his booking over the last 8 months.
So who would you pick to represent the faces in terms of physical might?